Unwanted by-catch is a serious problem around the world. Often, by-catch is discarded and results in direct food waste, and indirectly often influences biodiversity, stock abundance and long-term catch. To minimize by-catch problems, various fisheries management rules are applied, such as legal minimum sizes of landed fish, mesh sizes in fishing gears and closed areas. A more dramatic approach is to reduce the discards of unwanted catches by a landing obligation for all caught fish, independent of size and quality. For some years, this has been part of the fishery policy in countries such as Norway and Iceland. This chapter provides a framework for analysing the consequences of the landing obligation (LO). The empirical analyses of the economic consequences of the landing obligation give some insights into the impacts on the commercial fisheries. The examples look at the short-term impacts (no or limited behavioural changes) and the medium- and long-term impacts when fishing pattern and fleet size can be adjusted.